An endangered litter of piglets being eaten alive by their father, parrots on the loose in the city and a monkey drowning before being eaten by otters – it might all sound a bit far-fetched but these are all real events which happened at Bristol Zoo over the past few weeks.

The Bristol Post has learned that since December there have been three incidents at the zoo which led to animals dying or escaping from their enclosures.

One of the incidents has resulted in the loss of almost an entire family of critically endangered Visayan Warty Pigs, which are considered by the International Union for the Conservation of Nature as at extremely high risk of extinction in the wild in the near future.

Female warty pig Manilla arrived at the zoo in July, and was joined by a male called Elvis in September. At the time of Elvis's arrival, the zoo said it hoped the pair would become "proud parents" in the future.

But when Manilla gave birth, despite the fact that male warty pigs are known to be violent to the family, the parents were not kept separately, according to a whistleblower, and Elvis immediately ate the piglets.

A source told the Bristol Post: "On the day the female gave birth to piglets the male immediately ate them all, and then also attacked the mother by eating her rear end. She was so badly injured she had to be put down.

"This meant the loss of a family of rare warty pigs that could have been avoided by keeping the male separate."

The zoo confirmed that Manilla and the piglets had died, but said vets and keepers were unaware she was pregnant and described the incident as "completely unavoidable".

A spokeswoman for the zoo said: "Female warty pig Manilla arrived with us at the beginning of July last year.

"In November she showed some subtle changes to her behaviour and keepers alerted our in-house vet team.

"She showed no physical signs of being pregnant and, as she had not been with a male between July and October, she was well outside the known birth window for this species.

"The birth of her litter and the subsequent incident with the male was, therefore, completely unforeseeable."

However, just three weeks ago, another rare animal died after it managed to escape from its enclosure.

The whistleblower said: "Recently, a rare golden-headed lion tamarin escaped and fell into the nearby pond, where it was trapped in a drainage valve and then eaten by American otters."

Another of the zoo's escaped animals is still on the loose somewhere in the city.

A small hole in the lorikeet enclosure saw three of the birds escape last week.

The zoo managed to return two of the lorikeets, but one is still missing.

The source told the Post: "Three rainbow lorikeets escaped from their enclosure but only two were recovered. There is still one lorikeet loose somewhere in Bristol.

"If a breeding pair had escaped then Bristol may have been infested with birds."

The incidents have led the whistleblower to ask questions about the animals in care at the zoo.

But a spokesperson for BIAZA, which oversees and represents zoos and aquariums in the UK, said it was "extremely proud" of the zoo's high standards.

The zoo’s spokeswoman said recent incidents had been “distressing”, but the zoo was recognised as having some of the highest standards of animal welfare, education and conservation in Europe, as well as world-class in-house veterinary care.

She said: “We actively encourage natural animal behaviours and group dynamics. Our animals are also housed in natural enclosures, replicating environments they would be used to in the wild. As a result, on rare occasions, despite our best efforts, we are not able to prevent unfortunate and unforeseen situations from occurring.

“For example, three weeks ago a golden headed lion tamarin fell into the lake surrounding its island enclosure. The golden headed lion tamarin floated towards the otter enclosure, where it was taken in by a pair of otters. Our team of mammal keepers arrived at the location of the incident as soon as they could but unfortunately it was too late.

“The lorikeet enclosure is checked twice daily. In between the morning and afternoon check, three lorikeets escaped. The enclosure was checked and a small hole, covered with vegetation, was fixed immediately. Two of the birds have been recovered; efforts to return the third to the enclosure are ongoing.

“Our dedicated team of keepers and vets are committed to ensuring our animals receive the best care possible. Incidents such as these are distressing for the team and we are constantly seeking to improve our already high standards.

“We are a conservation charity committed to ensuring the survival of endangered species in the wild as well as in human care. Such incidents are distressing for zoo staff, particularly for the keepers who care for the animals involved.”

She added: “The zoo is inspected regularly under the Zoo Licensing Act and adheres to the strict animal welfare and husbandry guidelines laid out by British Association of Zoos and Aquariums (BIAZA) and Welfare Research Advisory Board (WRAB).”

The incidents have led the whistleblower to ask questions about the animals in care at the zoo, but a A spokesperson for BIAZA, which oversees and represents zoos and aquariums in the UK, said it was “extremely proud” of the zoo’s standards.

The spokesperson said: “As explained by the zoo, all of our members aim to actively encourage natural animal behaviours and group dynamics in their animal enclosures, which would include leaving animals together unless there is a clear reason to separate them. As far as possible they endeavour to replicate natural environments and habitats and as a result, on very rare occasions they are not always able to prevent unfortunate and unforeseen situations from occurring.

“Staff caring for these animals have been understandably distressed after these sad and unusual events, but we are confident that Bristol Zoo is doing everything possible to ensure that similar situations will not arise again in the future. As with all our members we’ll continue to assist and advise the zoo where necessary. Bristol Zoo’s a very active member of BIAZA and we’re extremely proud of their high standards and achievements in conservation, education, research and animal welfare.”